Make classes and structures in core/dom fast-allocated.

Source/core/dom/Microtask.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef Microtask_h
 #define Microtask_h
 
 #include "bindings/core/v8/ScriptState.h"
 #include "core/CoreExport.h"
 #include "public/platform/WebThread.h"
+#include "wtf/Allocator.h"
 #include "wtf/Functional.h"
 #include "wtf/PassOwnPtr.h"
 #include <v8.h>
 
 namespace blink {
 
 class CORE_EXPORT Microtask {
+    STATIC_ONLY(Microtask);
 public:
     static void performCheckpoint(v8::Isolate*);
     static bool performingCheckpoint(v8::Isolate*);
 
     // TODO(jochen): Make all microtasks pass in the ScriptState they want to be
     // executed in. Until then, all microtasks have to keep track of their
     // ScriptState themselves.
     static void enqueueMicrotask(PassOwnPtr<WebThread::Task>);
     static void enqueueMicrotask(PassOwnPtr<Closure>);
-
-private:
-    explicit Microtask();
 };
 
 } // namespace blink
 
 #endif // Microtask_h